1. Technical Field
The present technology relates to a rubber composition for use in tires, and more particularly relates to a rubber composition for use in tires having grip performance on both icy and snowy road surfaces and wet road surfaces enhanced to or above conventional levels.
2. Related Art
Pneumatic tires for use on icy and snowy roads (studless tires) are designed to enhance grip performance by increasing adhesion force to icy and snowy road surfaces by maintaining hardness of a tread rubber while still remaining pliable, even at low temperatures. Additionally, in recent years, there has been a demand for studless tires having enhanced traveling performance on wet road surfaces that are not covered with ice and/or snow as well as travelling performance on icy and snowy road surfaces as described above. Conventionally, a styrene butadiene rubber having a high glass transition temperature (Tg) has been compounded in order to enhance the wet grip performance. However, when a styrene butadiene rubber having a high Tg is compounded, the Tg of the entire rubber composition increases, which leads the adhesion force to icy and snowy road surfaces being negatively affected due to an increase in a rubber hardness at low temperatures.
To resolve this problem, Japanese Unexamined Patent Application Publication No. 2007-321093 proposes enhancing braking performance on wet road surfaces and on ice by compounding 100 parts by weight of a diene rubber including from 20 to 80 weight % of a natural rubber and/or an isoprene rubber and from 80 to 20 weight % of a butadiene rubber with a terpene resin having a glass transition temperature of −10° C. or lower. However, this rubber composition still has room for further improvement because it has not sufficiently satisfied the demands for higher levels of both travelling performance on icy and snowy road surfaces and travelling performance on wet road surfaces.